Possibly I am the Mike Steve is he he-ing at so I better type something out, [Soon I guess Steve will switch to a more seasonal Ho Ho. ] In an ideal world you only use manufacturer's fresh paste straight out of the jar and therefore guaranteed to be in as specified condition. In a highly mixed line this can be difficult as it can take more paste to load the squeegee than you are going to use. The key to controlling solder paste on the shop floor is to control the rate of issue and to match (if possible) the container size to amount used per work period. In other words only take out of stores that which you are going to use in the next shift or half shift and order a container size which will get used up. That way you won't have any left over. Easier said than done, but its a start point for thinking. How much you deviate from this depends on how much you can trust your people to carry out procedures and how much effort you want to put in to save a few dollars worth of material against the risk of using out of spec material. The knack is to devise a system that is not too discretionary for operators and is simple to do. I suggest this is related to time not number of times used or usage. When thinking what you are going to do, keep in mind that temperature cycling paste in and out of cold store is very like an artificial ageing regime. I suggest an ideal system would therefore have these elements. Set up a system of bulk storage in main stores, a weekly store on shop floor and a day store on /near machine. Impress this is one way only. At the beginning of the week move from bulk (very cold if required) to shop floor storage. (simple refrigerator if required) Each day (or night before if refrigerated) the amount for next day. Put a colour blob on each container corresponding to the day of the week. (Monday blue, Tuesday green and so on) IF you have really light usage write on the day date of first use. Now you [without overt supervision] - and operators - can see what jars are in use and if they are out of time. And make simple rules to change jars. Backwards moving jars are easily spotted by the blobs etc. Clear out the machine/local store periodically. Now you can feel a little more comfortable about saying things like load squeegee with today's paste and replenish with paste no more than one day old etc. Never use more than one third old paste with new. Your actual supplier can give you some ideas/ratios, experience will tell you the rest. Hope this helps Regards Mike Fenner Applications Engineer, Indium Corporation -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Steve Gregory Sent: Tuesday, December 03, 2002 1:35 AM To: [log in to unmask] Subject: [TN] Solderpaste life... Hi all! Hope everybody had a good thanksgiving holiday (our USA members anyway), but have a question about solderpaste life. We are a low-volume, high mix shop, and we may run 5-20 assemblies, then switch over to another assembly. The solderpaste between these switch-overs may change from a high activity OA to a low activity no-clean depending on the requirements called out on the assembly drawing. In the past, we have chosen the path, that once solderpaste is opened, it is either used, or scrapped. But looking closely at this policy, we're throwing a lot of paste away, and maybe we shouldn't. It's no small change, when I've looked at how much we throw away...just wondering now, and I understand the issues of using very old solderpaste, and mixing fresh with new, but does anybody have any guidelines of when they throw paste away, or put it back in the jar to reuse? I'm about to write some procedures concerning this. I don't think that once the jar, or container is opened, it needs to be consumed all at once, or scrapped. I do think solderpaste is a bit more robust than that (but you might have a hard time for the vendors to say that...hehehe....sorry Mike!). I do think that if good control is maintained, solderpaste can perform as advertised, whether it has been opened previously or not... Just curious if anybody else has encountered this issue...and adressed it. -Steve Gregory- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------